Purchase requisition not converting into PO in APO (PPDS)

Hello Gurus,

I am new in APO, user is facing issue while converting the purchase requisition into PO but failed.

User create a purchase requisition in /sapapo/rrp3, and set a conversion indicator.

But its not converting to PO after refresh several times.

I have already check the t-lane, PIR, material master data.

Could you please guide me on this, what I need to check or maintain?

Thanks

Saniket